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Linux

概述

Linux 是一种开源的类 Unix 操作系统，包括许多不同的版本，诸如 CentOS、Ubuntu 等。

安装

下载 CentOS 或 Ubuntu 的 ISO 镜像。除了服务器，也可以安装在虚拟机上，比如 VMware。

远程连接

使用 XShell 可以通过 SSH（Linux 通常自带 SSH）远程连接 Linux 服务器。查看 SSH 状态：service sshd status，如果没有，可以按照如下命令安装：

yum install openssh-server  # 安装 SSH
vim /etc/ssh/ssh_config     # 编辑配置文件
/bin/systemctl start sshd.service   # 启动 SSH 服务
/bin/systemctl enable sshd.service  # 开机自启动

大部分的远程连接（比如 MySQL 和 Redis）都支持 SSH，此时，SSH 需要配置为允许 TCP 连接：AllowTcpForwarding yes。

镜像

国内可以修改软件服务镜像为 aliyun：

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo # base
wget -O /etc/yum.repos.d/epel-7.repo http://mirrors.aliyun.com/repo/epel-7.repo  # epel
yum clean all  # 更新镜像
yum makecache  # 创建缓存

目录结构

RPM 结构的目录结构通常设置如下：

  • /etc: 配置文件
  • /usr/bin: 可执行文件
  • /usr/lib: 动态库
  • /usr/share/doc: 用户文档
  • /usr/share/man: 帮助文档

Get Started

Linux 是一个权限管理的多用户系统. 使用命令 su 从普通用户切换为 root 身份，使用命令 exit 以退出。

开发工具

安装常见的开发工具

yum -y groupinstall "Development tools"
yum install -y bash-completion vim lrzsz wget expect net-tools nc nmap tree dos2unix htop iftop iotop unzip telnet sl psmisc nethogs glances bc

System and Partitions

Each hardware device in Linux is regarded as a file. They are almost all under /dev directory.

Service

Relative commands are shown as follows:

/bin/systemctl start <service>
service <service> status
/bin/systemctl enable <service> # start at startup

User and Privilege

  • id show ids
  • useradd add a new user
  • passwd [username] change password for users

Files and Directories Management

Path

Absolute paths start with the root path /, such as /usr/share/doc. But on the contrary, relative paths don't start with /, share/etc for example.

Commands

Use -help to list some options of the command or use man/info commands to show details, such as man cd. Following are some common commands.

Directory

  • cd change directory
  • pwd print working directory
  • mkdir make a directory by a level. Append -p after the command if recursion is required.
  • rmdir remove an empty directory by a level. Append -p if recursion is required.

Operator

  • ls list
  • cp copy
  • rm remove
  • mv move

Text Document

  • cat concatenate content of file
  • tac concatenate content in reverse direction
  • nl print with line numbers
  • more print one page. Click Space to next page or Enter to next line.
  • less familiar to more
  • head defaults to the first 10 lines
  • tail familiar to head

Upload and Download

Install toolkit rz and sz by yum install lrzsz. Then use commands rz to upload or sz to download. Target files will be upload to current directory.

Vim

Misc

Firewall

The service name is firewalld and the command is firewall-cmd.

Open the specific port when remote connections are refused.

firewall-cmd --zone=public --add-port=<port/tcp> [--permanent]

FAQ

Pane is dead

If it occurs to Pane is dead when installing, open settings of hardwares and then change CD/DVD (IDE) connection to the path of the ISO file.

Connect to Internet

If failed, open settings of current network connection of the host and allow Internet Connection Sharing.

Static IP

Edit the /etc/sysconfig/network-scripts/ifcfg-ens33 file:

BOOTPROTO="static"
IPADDR=<ip>
NETMASK=255.255.255.0
GATEWAY=<gateway> # same as that of the host
DNS1=<dns1> # also same as those of the host
DNS2=<dns2>

参考